The disclosure of Japanese Patent Application No. 2002-154668 filed on May 28, 2002 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to vibration damping bushings for use in a part connecting a suspension with a body of an automotive vehicle, or the like, and more particularly relates to such a vibration damping bushing configured to exhibit relatively hard spring characteristics in a radial direction at a specific circumferential position.
2. Description of the Related Art
A vibration damping bushing of this kind typically includes a tubular elastic body interposed between a rigid inner sleeve and a rigid outer sleeve. The inner and outer sleeves are respectively affixed to one and the other of two components that are to be linked together, e.g., a suspension and a body of an automotive vehicle.
Where the inner sleeve, outer sleeve, and elastic body are of uniform shape all the way around their circumference, a vibration damping bushing of this kind may exhibit spring characteristics uniform in every radial direction. More specifically, the spring characteristics of the vibration damping bushing caused by elastic deformation of the elastic body in radial directions will be uniform, for all the cases whether the inner sleeve undergoes upward, downward, rightward and leftward displacements relative to the outer sleeve, for example.
However, a vibration damping bushing of this kind may be desired, for example, to have hard spring characteristics when the inner sleeve undergoes upward displacement relative to the outer sleeve, and to have soft spring characteristics when it undergoes downward displacement, or to have hard spring characteristics when undergoing rightward displacement and soft spring characteristics when undergoing displacement in the opposite leftward direction. Namely, the vibration damping bushing may be required, depending on the location at which the vibration damping bushing will be used, to exhibit spring characteristics being hard in a radial direction located at a specific circumferential position, while being soft in an opposite radial direction or some other radial directions.
To meet this requirement, there have been a considerable number of proposals to provide the elastic body with hollow portions (through holes) or to modify the shape of the hollow portions. FIG. 7 shows an example of such a conventional bushing, i.e., a vibration damping bushing 200, as disclosed in JP-A-7-286634.
The vibration damping bushing 200 as shown in FIG. 7 is of so-called inner/outer sleeve-bonded type in which a tubular elastic body 206 is bonded to a rigid inner sleeve 202 and outer sleeve 204. The elastic body 206 is provided with hollow portions (through holes) 208, 210 situated at respective positions above and below the inner sleeve 202. The hollow portions 208, 210 differ in shape from each other. As a result, the vibration damping bushing 200 exhibits different spring characteristics in opposite radial directions, depending on whether the inner sleeve 202 undergoes upward displacement or downward displacement relative to the outer sleeve 204.
In a vibration damping bushing of this inner/outer sleeve-bonded type, it is a relatively simple matter to make radial spring characteristics thereof differ between, for example, the upward direction and the downward direction, by forming hollow portions like those described above or modifying the shape of the hollow portions.
Also known are press fit type bushings, which do not have an outer sleeve at the time when the elastic body is molded, instead, the bushing is assembled by press fitting the elastic body at its outer circumferential surface into a tubular part provided to one of the two components, e.g., a suspension arm. In this case, it is difficult for the bushing to make radial spring characteristics hard in a specific direction and soft in another direction by forming hollow portions through the elastic body or modifying the shape of the hollow portions. The reason is that the presence of such hollow portions in an elastic body makes it difficult to assure adequate bonding force by means of press fitting.
It is therefore one object of this invention to provide a vibration damping bushing whose radial spring characteristics is made hard at a desired circumferential position.
The above and/or optional objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A vibration damping bushing for connecting a first and a second component in a vibration damping fashion, comprising: (a) a rigid inner sleeve fixable to a first component; (b) a rigid outer sleeve fixable to a second component; (c) an elastic body having a main body portion of tubular configuration interposed between said inner and outer sleeves; (d) a pair of flange portions integrally formed at opposite axial end portions of said main body portion, extending radially outwardly and laminated on opposite axial end faces of said outer sleeve, respectively; and (e) a deformation resistant portion provided for at least one of said pair of flange portions over a given circumferential length, said deformation resistant portion projecting axially outwardly to be opposed to a member of said first component with a spacing therebetween, wherein said flange portion undergoes elastic deformation toward said member of said first component due to compressive deformation of said main body portion in radial directions perpendicular to an axial direction of said bushing so that said deformation resistant portion comes into contact with said member of said first component to increase deformation resistance of said elastic body.
According to this mode of the invention, a vibration damping bushing is configured such that the flange portion is caused to deform towards the member of the first component by means of compressive deformation of the main body portion in radial directions, and a portion of the flange extending over the predetermined range in the circumferential direction thereof constitutes the deformation resistant portion. In this vibration damping bushing, when the inner sleeve undergoes displacement relative to the outer sleeve toward the side provided with the deformation resistant portion, in other words, when the main body undergoes compressive deformation on the side where the deformation resistant portion is provided, the deformation resistant portion is forced to come into contact with the member of the first component, thus creating strong deformation resistance. As a result, increased is compressive deformation resistance in the main body portion, making the spring characteristics of the vibration damping bushing harder at a specific circumferential position, namely at the portion provided with the deformation resistant portion. It should be noted that the member of the first component includes the first component itself, a bracket to be fixed to the first component for fixedly mounting the inner sleeve on the first component, and other members fixed to the first component.
Preferably, at least one of the pair of flange portions has an axial wall thickness that is made large at a predetermined circumferential position thereof over the given circumferential length so as to provide the deformation resistant portion protruding axially outwardly beyond an axial end face of the at least one of the pair of flange portions.
(2) A vibration damping bushing according to the above-indicated mode (1), wherein the vibration damping bushing is of press fit type in which the elastic body is press fitted and secured at an outer circumferential surface thereof to an inner circumferential surface of the outer sleeve.
Advantages of the invention according to this mode can be well enjoyed at a vibration damping bushing of press fit type rather than of inner/outer sleeve-bonded type.
(3) A vibration damping bushing according to the above-indicated mode (1) or (2), wherein the deformation resistant portion is provided with a recess open in protruding end faces thereof.
According to the present invention, the deformation resistant portion may have the same axial wall thickness over its entire circumference, or alternatively may have the axial wall thickness vary in its circumferential direction, which may be embodied by forming the recess open in the protruding end faces of the deformation resistant portion according to this mode (3). In the former case, the deformation resistant portion comes into contact with the member of the first component over a substantially entire area of its protruding end face. In the latter case, however, the part of the deformation resistant portion comes into contact with the member of the first component, effectively eliminating or reducing possibility of ocurrence of noises generated upon abutting contact of the deformation resistant portion against the bracket, which would be caused by the overall contact of the deformation resistant portion against the bracket, or rubbing of the deformation resistant portion against the bracket. It is also possible to form a plurality of recesses onto the deformation resistant portion. In this case, the recesses may be arranged in the circumferential direction of the flange portion in regular intervals.
(4) A vibration damping bushing according to any one of the above-indicated modes (1)-(3), wherein a radial wall thickness of the main body portion of the elastic body is made small on a side where the deformation resistant portion is provided.
According to the mode (4) of the invention, the vibration damping bushing can exhibit hard spring characteristics at a specific radial direction lying on the circumferential position where the deformation resistant portion is provided.
(5) A vibration damping bushing according to the above-indicated mode (4), wherein a center axis of the inner sleeve is eccentric relative to a center axis of the elastic body toward the side provided with the deformation resistant portion so that the radial wall thickness of the main body portion of the elastic body is made small on the side provided with the deformation resistant portion.
This mode of the invention makes it facilitate to reduce the radial wall thickness of the main body portion of the elastic body on the side where the deformation resistant portion is provided, by simply offsetting the center of the inner sleeve relative to the center of the elastic body towards the deformation resistant portion provided side.